Rheinwg
The Kingdom of Rheinwg was a Brittonic kingdom, in the south of modern-day Wales, which is often thought to have been a union of the kingdoms of Dyfed and Brycheiniog
History
Rheinwg emerged during the early medieval period as a territorial designation for the expanded kingdom of Dyfed, which incorporated Brycheiniog by the 8th century. The union originated under Dyfed and Brycheiniog">Kingdom of Dyfed">Dyfed and Brycheiniog, who married Ceindrych, heiress of Brycheiniog, consolidating both regions under a single dynasty. This union persisted until the early 8th century, when Rhain ap Cadwgan ruled the combined realm.The kingdom’s territorial integrity was challenged by Seisyll of Ceredigion, who annexed Ystrad Tywi c. 710 CE. The remaining territories of Dyfed and Brycheiniog were subsequently termed Rheinwg, likely named after Rhain ap Cadwgan. By the 12th century, Rheinwg’s geographic scope had become obscure, with later scholars misinterpreting its boundaries. According to the Annales Cambriae Rheinwg was devastated by Offa of Mercia in 797.